<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        var arr = ['a', 'b', 'c', 'd', 'e'];

        //   arr.forEach(function(value, index, array) {
        //        //参数一是:数组元素
        //        //参数二是:数组元素的索引
        //        //参数三是:当前的数组
        //  })
        var rel = arr.forEach(function(value, index, array) {
            console.log(value);
            console.log(index);
            console.log(array);
        });
        // forEach方法没有返回值
        console.log(rel);
    </script>
</body>

</html>